Color stabilization of fatty materials



Patented Mar. 30, 1954 UNITED STATES TENT OFFICE COLOR STABILIZATION FFATTY MATERIALS Illinois No Drawing. Application June 21, 1951, SerialNo. 232,869

7 Claims. (Cl. 260-398.5)

The present invention relates in general to a method of preventing colorreversion in fatty materials, and more particularly to a method forstabilizing fatty materials, decolcrized by treatment with a liquefiednormally gaseous hydrocarbon, so as to prevent subsequent colorreversion of the decolorized fatty material.

The use of propane or other liquefied, normally aseous hydrocarbons,such as ethane, butane or mixtures thereof, to remove colored impuritiesfrom fats and fatty acids is known to the prior art and has beendescribed in U. S. Patents 2,118,454; 2,219,652; 2,383,535; and2,367,671. Essentially, the process comprises dissolving the fattymaterial under pressure in several volumes of a liquefied, normallygaseous hydrocarbon maintained at elevated temperatures and pressureswhereby two phases are formed--the lighter phase containing thedecolorized fatty material and the heavier or lower phase containingcolor bodies and tarry impurities. The upper phase is removed and thehydrocarbon separated from the fatty material by means of distillationto produce a decolorized product. Preferably, the process is carried outas a continuous countercurrent process for most efficient results.

It has been found that when a fat such as an inedible tallow or the likeis decolorized by treatment with a liquefied, normally gaseoushydrocarbon, it has a pronounced tendency to darken or color-revertappreciably when kept hot and exposed to air. Normal fat antioxidantsadded to the fatty material after decolorization do not materiallyimprove the color reversion situation. A major reason for theineffectiveness of antioxidants in general as color stabilizers is dueto the fact that oxidation is but a small part of color reversion.Antioxidants, in general, are of little value as color stabilizers, andthe stabilization against color reversion of low-grade fats which havebeen, or are to be, propane-decolorized presents a much more dimcultproblem than the stabilization of a high-grade fat to oxidation.

It is, therefore, an object of the present invention to provide a methodfor stabilizing fatty material against color reversion.

It is another object of the invention to provide a method forpretreating inedible fatty stock to be decolorized by treatment with aliquefied, normally gaseous hydrocarbon to prevent subsequent colorreversion of the decolorized fatty material.

It is a further object of the invention to provide a method forstabilizing inedible fatty materials, which have beenpropane-decolorized, against color reversion.

Additional objects, if not specifically set forth herein, will bereadily apparent to one skilled 2 in the art from the following detaileddescription of the invention.

The present invention in general is based on the discovery thathypophosphorous acid will effectively stabilize the color reversion offatty materials which have been decolorized by treatment with aliquefied, normally gaseous hydrocarbon. I'he hypophosphorous acid maybe added to the fatty material after decolorization or preferably to thefatty stock prior to decolorization. This latter preferred methodproduces a decolorized product which is far more stable than a'productwhich has been decolorized without pretreatment.

When used for pretreating the fatty stock, the hypophosphorous acidshould be added in an amount around 1 per cent by weight or more of thefatty stock, and the treated stock held for preferably about 4. hours atan elevated temperature before decolorizing. This holding period hasbeen found to provide substantial improvement to the color-stability ofoils containing the hypophosphorous acid. The time of holding may varydepending on the temperature of holding and on the amount ofhypophosphorous acid employed. A holding period of at least 1 hour ataround. 200 F. is required, and preferably as indicated above, a 4-hourholding period is employed. The holding temperature may vary from about180 F. to about 268 F. The hypophosphorous acid may be added to thestock in the form of a 50 per cent aqueous solution desired. Preferably,the treated stock is then held overnight at about 149 F. to settle, thefoots drawn off, and the acid-washed oil decolorized.

When used as an additive to fatty materials after decolorization bytreatment with a liquefied, normally gaseous hydrocarbon, theconcentration of hypophosphorous acid should be about 0.5 per cent byweight of the fatty material. In practice, the hypophosphorou acid maybe added manually to the decolorized fatty materials and thoroughlymixed therewith, or preferably added through a proportioning pump or thelike into the decolorized product as it leaves the decolorizingoperation. The fatty material to which the hypophosphorous acid is addedmust be about 1030 F. above the temperature at which it is completelyliquid (about -175 F. depending on the particular fatty material beingtreated). Decolorized oils, after processing, are kept at thesetemperatures, 1. e. 10-30 F. above the point at which they are fluid,only long enough to accumulate an amount sufiiciently large to pump toan empty tank car or storage tank, after which the oils are allowed tocool and solidify. This means that in plant operations, such fattymaterials will ordinarily be held at l40-175 F. from 24 to 48 hours.Laboratory testing was carried out at aggravated temperature conditionsin order to accelerate any reversion tendencies of the fatty materialstreated in accordance with the present invention. The concentration ofhypophosphorous acid may vary from about 0.3 per cent up to about 1.0per cent depending on the fatty material treated. Storage at 140 F., asillustrated in Example If and simulating plant holding conditions,resulted in an initial reversion of one FAC color unit, followed by areturn to the original color. Storage at higher temperatures (200 F.) inclosed containers to provide accelerated reversion conditions resultedin a direct bleach of from 1 to 3 FAG color units. Samples were storedin e-ounce oil sample bottles, stoppered and unstoppered. Stabilizedsample containing less than 90 per cent f. f. a. were stored with asmall piece of black iron wire to simulate plant conditions whereindecolorized fats are stored in iron tanks.

The percentage of hypophosphorous acid required is relatively large,ranging from about 6.3 per cent to about 1.0 per cent by weight of thefatty material when used as an additive after decolorization. When usedin pretreating the fatty materials to be decolorized at least about 1.0per cent by weight is desirable although larger or smaller amounts arebeneficial, the larger amount usually being limited by economicconsiderations.

It has been found that hypopiiosphorous acid alone and not the saltsthereof will function to inhibit color reversion. It functions equallywell under an air or inert gas atmosphere, thus indicating that it isnot a deoxygenating process.

The following examples, utilizing propane as the liquefied, normallygaseous hydrocarbon, are furnished for the purpose of illustration only:

Example I Acidulated soybean foots were pretreated with hypophosphorousacid by agitating the foots with 1.0 per cent hypophosphorous acid for 4hours at HEW-200 F. The stock was allowed to settle overnight at about140 F. and the foots drawn off. This material was then subjected tocounter-current propane decolorizing at 200 R, 679 p. s. i. g. and a25:1 propane to fat ratio. The overhead product recovered had an FAGcolor of 9-11A.

Erample If Samples of decolorized fatty materials from. the propanedecolorizing operation were treated with varying percentages ofhypophosohorous acid and held at 145? F. until signs of color reversionappeared. The following table shows the results of this treatment:

Percent 31 llecolorized Fatty Material tarot flfitfi Added. (days) 0. 154 1. 0 2 54 0. 3 3 Yellow grease 0. 5 29 butane or mixtures thereof.The term "fatty maerials as used in the appended claims is intended tocover animal fats, particularly inedible greases and tallows; fattyacids, such as tallow fatty acids, stearic acid, and soybean foots fattyacids; and vegetable fats and oils, for example, soybean and cottonseedoils, soybean and cottonseed foots, and the like.

Although the invention has been described in connection with thetreatment of fatty materials decolorized or to be decolorized withnormally gaseous hydrocarbons, it is also applicable to treatment offatty materials subject to decolorization with other decolorizingsolvents as, for example, acetone, methyl ethyl ketone and loweraliphatic liquid hydrocarbons, such as butane or isobutane, etc.

Obviously, many modifications and variations of the inventionhereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

I claim:

1. A method for inhibiting color reversion in fatty materials which havebeen decolorized by treatment with a liquefied normally, gaseoushydrocarbon which comprises incorporating in said fatty materials whilein the liquid state a small amount of hypophosphorous acid.

2. A method as in claim 1 wherein the hypophosphorous acid is present infrom about 0.3 per cut to about 1.0 per cent by weight of the fattymaterial.

3. A method for inhibiting color reversion in fatty materials which areto be decolorized by treatment with a liquefied, normally gaseoushydrocarbon comprising incorporating with said fatty materials prior todecolorization a small amount of hypophosphorous acid, maintaining saidfatty materials so treated at an elevated temperature for at least 1hour, and thereafter subjecting said fatty materials containing saidhypophosphorous acid to a decolorization treatment with a liquefied,normally gaseous hydrocarbon.

4. A method as in claim 3, wherein the hypophosphorous acid is presentin about 1.0 per cent by weight of the fatty material.

5. A method for inhibiting color reversion in fatty materials, whichcomprises incorporating with said fatty materials a small amount ofhypophosphorous acid, maintaining said fatty material containing saidacid at about l200 F. for at least 1 hour, and thereafter subjectingsaid fatty material containing said acid to a countercurrentdecolorizing operation with a liquefied, normally gaseous hydrocarbon.

6. The improvement in the liquefied, normally gaseous hydrocarbondecolorization and stabilization to color reversion of fatty materials,which comprises treating sai fatty materials with a small amount ofhypophosp-horous acid.

7. A method for inhibiting color reversion in fatty materials which havebeen decolorized by treatment with liquefied normally gaseous propanewhich comprises incorporating in said fatty materials while in theliquid state a small amount of hypophosphorous acid.

ROBERT J. I-ILAVACEK.

Name Date Heuser Aug. 18, 1925 Number

1. A METHOD FOR INHIBITING COLOR REVERSION IN FATTY MATERIALS WHICH HAVEBEEN DECOLORIZED BY TREATMENT WITH A LIQUEFIED NORMALLY, GASEOUSHYDROCARBON WHICH COMPRISES INCORPORATING IN SAID FATTY MATERIALS WHILEIN THE LIQUID STATE A SMALL AMOUNT OF HYPOPHOSPHOROUS ACID.